A long-term experiment in growing ash, walnut, oak and beech trees is being carried out at a specially planted wood in Oxfordshire.

Paradise Wood, on 135 acres of former farmland below Wittenham Clumps, is the centre for forestry research and training — the only one of its kind in Europe —with some 42 separate tree-impriovement trials.

Set up in the early 1990s at College Farm, Little Wittenham, the work is being undertaken on the initiative of the Northmoor Trust in conjunction with the British and Irish Hardwoods Improvement Programme.

Most of the trees have been planted thanks to grants from the Forestry Commission.

In brief, the research is being conducted to improve the vigour and form of our native broadleaved trees, to reduce rotation times and to increase the amount of recoverable timber.

This is important if trees other than our traditional oak, beech and conifers can be developed to improve the country’s stock of trees for the timber trade, because the country imports far more timber than it can produce.

If more quality timber can be grown here, then our imports could be reduced.

To assess the effects of soil and weather on the growth of trees, similar blocks or stands of trees to those at Little Wittenham have been planted in different parts of the country.

Jo Clark, forestry research manger for the Northmoor Trust, said: “If we test trees on the fertile soil of the Welsh Marches only, then they may not grow as well on poorer soils elsewhere.

“We have planted out woods across the UK at Hungerford in Berkshire, Gloucestershire, Yorkshire and Inverness.

“But these woods are not necessarily as extensive as we have at Paradise Wood because we rely on other farmers and landowners allocating land.”

She added that a traditional tree breeding programme could increase genetic diversity of a population of trees, making them more robust to disease.

It had already been discovered that a wood of a mix of different species of trees could slow up the spread of diseases.

To make the experiment more comprehensive, woods have also been planted in northern France and in the Pyrenees in Spain.

Altogether, ten experimental woods have been planted on a longitudinal gradient or line from Inverness to the Pyrenees.

Jo added: “Each population of trees is planted at each trial site so that we can see how our native ash will cope with the French climate and how the French ash will cope with our climate.”

It is thought that by 2050 our climate might be like the Loire Valley in France and by 2080 it could be similar to the climatic conditions of the south of France.

Trees are checked regularly to compare their growth and to find out how resistant they are to the weather and disease.

An instance of how the weather affects trees has been found at Paradise Wood where walnuts growing close to a high hedge are growing better than those further away from the protection of the sheltering hedge.

And a frost that rolls down the hillside from Wittenham Clumps can affect some of the trees.

“This is a long-term project that is expected to take at least 40 years before we get the results we are looking for,” said Jo.

The Northmoor Trust project was begun by Jo’s predecessor Dr Gabriel Hemery, who went on to co-found the Sylva Foundation, which is also based at Little Wittenham.

One of the species chosen by Dr Hemery with which to experiment was walnuts and he travelled to the Kyrgzy walnut forest in Kazakhastan, a former Soviet republic.

He collected some 2,000 walnut seeds which he germinated at his home and they were brought on at Nicholsons Nurseries at North Aston, near Bicester, before being planted out at Paradise Wood.

The Sylva Foundation is involved in several woodland and forestry management programmes with landowners and the One Oak project, which involves schoolchildren experiencing woodland through studying the life of an oak.